Structures, lithographic mask forming solutions, mask forming methods, field emission display emitter mask forming methods, and methods of forming plural field emission display emitters

ABSTRACT

The present invention includes structures, lithographic mask forming solutions, mask forming methods, field emission display emitter mask forming methods, and methods of forming plural field emission display emitters. One aspect of the present invention provides a mask forming method including forming a masking layer over a surface of a substrate; screen printing plural masking particles over a surface of the masking layer; and removing at least portions of the masking layer using the masking particles as a mask. Another aspect of the present invention provides a method of forming plural field emission display emitters. This method includes forming a masking layer over an emitter substrate; screen printing a plurality of masking particles over the masking layer; removing portions of the masking layer intermediate the screen printed masking particles to form a plurality of masking elements; removing the masking particles from the masking elements; and removing portions of the emitter substrate to form plural emitters.

PATENT RIGHTS STATEMENT

[0001] This invention was made with Government support under ContractNo. DABT63-97-C-0001 awarded by Advanced Research Projects Agency(ARPA). The Government has certain rights in this invention.

TECHNICAL FIELD

[0002] The present invention relates to structures, lithographic maskforming solutions, mask forming methods, field emission display emittermask forming methods, and methods of forming plural field emissiondisplay emitters.

BACKGROUND OF THE INVENTION

[0003] Field emission displays are utilized in a variety of displayapplications. Conventional field emission displays include a cathodeplate having a series of emitter tips fabricated thereon. The tips areconfigured to emit electrons toward a phosphor screen to produce animage. The emitters or emitter tips are typically formed from an emittermaterial such as conductive polysilicon, molybdenum, or aluminum.Multiple emitters are typically utilized to excite a single pixel. Forexample, 120 emitters may be used for a single pixel. Individual pixelscontain a deposited one of red, green, or blue phosphor.

[0004] One method of fabrication of emitter tips is described in U.S.Pat. No. 5,391,259 (the '259 patent); assigned to the assignee hereofand incorporated by reference. A hardmask layer is formed over emittermaterial in the disclosed fabrication method. Portions of the hardmasklayer are selectively removed to form a hardmask utilized for emitterfabrication. One conventional method utilizes photolithography andetching to selectively remove portions of the hardmask layer. Followingthe formation of the hardmask, the emitter material is etchedisotropically to form the tips. For proper fabrication, it is highlydesired that hardmasks be patterned to a consistent critical dimension.Variations in critical dimensions or size of the hardmasks can result innon-uniformity within the formed emitter tips.

[0005] One method for fabricating the hardmask utilized to form theemitter tips uses spheres or beads as the mask for creating the hardmasklayer mask. The spheres are provided in a liquid medium such as water.The emitter substrate is dipped into a vat of solution containing thespheres. The substrate is then withdrawn from the solution and some ofthe spheres adhere to the emitter substrate.

[0006] It is preferred to achieve a homogeneous/uniform distribution ofbeads upon the face of the emitter material. However, homogeneousdistribution has been difficult to achieve. A non-uniform distributionof beads can result in adjacent spheres touching and subsequentadjoining of emitter tips following emitter fabrication causing problemswith electron optics (e.g., focusing of electrons). Such joining ofemitter tips can result in the emission of electrons which strikeadjacent phosphor patches resulting in poor color intensity and poorcolor distribution.

[0007] Further, the spheres may exhibit poor adhesion to the surface ofthe substrate when conventional methods of applying the spheres to thesubstrate surface are utilized. This drawback is particularly acute ifthe spheres are larger than 0.5 microns.

[0008] The present invention provides improvements in device fabricationwhile avoiding problems experienced in the prior art.

SUMMARY OF THE INVENTION

[0009] The present invention includes structures, lithographic maskforming solutions, and mask forming methods. The invention furtherincludes field emission display emitter mask forming methods and methodsof forming plural field emission display emitters.

[0010] One aspect of the present invention provides a lithographic maskforming solution. The solution includes a photosensitive material and aplurality of masking particles within the photosensitive material. Thephotosensitive material comprises photoresist and the masking particlescomprise beads or spheres in exemplary embodiments. The photosensitivematerial is cured and portions of the cured photosensitive material areremoved in preferred aspects of the invention. Masking particlesremaining upon the substrate are thereafter used as a mask to process asubstrate. Uncured photosensitive material is used to improve adhesionof masking particles to the substrate to be processed.

[0011] A second aspect of the invention provides a structure formingmethod including providing a solution comprising a photosensitivematerial and a plurality of masking particles. The method also providesapplying the solution over a substrate and removing at least a portionof the photosensitive material while leaving the masking particles overthe substrate. The solution is preferably screen printed. The methodalso includes processing the substrate using the masking particles as amask.

[0012] According to another aspect, a method of forming a mask over asubstrate includes forming a masking layer over a surface of asubstrate. Masking particles are screen printed over a surface of themasking layer and portions of the masking layer are removed using themasking particles. The removing of portions of the masking layer forms amask. This mask includes a plurality of circular masking elements insome embodiments.

[0013] In another aspect, masking particles are mixed within photoresistto form a solution which can be screen printed. The screen printingincludes printing masking particles within the solution containingphotoresist. In one embodiment, the solution has a concentration withinthe approximate range of approximately 1×10⁸-1×10⁹ masking particles permilliliter of photoresist.

[0014] It is preferred to provide a uniform layer of masking particlesupon the masking layer. To this end, screen printing of maskingparticles guides the masking particles to predefined regions over thesubstrate. Further, the masking particles are preferably agitated tospace the masking particles from one another.

[0015] In some aspects of the invention, the solution is permitted tocure and portions of the photoresist or other photosensitive material isremoved. The masking particles form a mask utilized to form a hardmaskfrom the masking layer. The hardmask is subsequently utilized to form arandom array of emitters of a field emission display from an emittersubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

[0017]FIG. 1 is a cross-sectional view of a structure including asubstrate and a solution layer during processing of the structure.

[0018]FIG. 2 is a cross-sectional view of a processing step of thestructure subsequent to the step of FIG. 1.

[0019]FIG. 3 is a cross-sectional view of a processing step of thestructure subsequent to the step of FIG. 2.

[0020]FIG. 4 is a cross-sectional view of a segment of a field emissiondisplay having plural emitters fabricated in accordance with processesof the present invention.

[0021]FIG. 5 is a cross-sectional view of a substrate, masking layer,layer of solution and a screen during fabrication of a backplate of afield emission display.

[0022]FIG. 6 is a diagrammatic representation of conventional offsetscreen printing.

[0023]FIG. 7 is a diagrammatic representation of contact screenprinting.

[0024]FIG. 8 is a top plan view of a predefined region shown at theprocessing step of FIG. 5.

[0025]FIG. 9 is a cross-sectional view of a processing step for formingthe backplate subsequent to the step of FIG. 5.

[0026]FIG. 10 is a cross-sectional view of a processing step of thebackplate subsequent to the step of FIG. 9.

[0027]FIG. 11 is a cross-sectional view of a processing step of thebackplate subsequent to the step of FIG. 10.

[0028]FIG. 12 is a cross-sectional view of a processing step of thebackplate subsequent to the step of FIG. 11.

[0029]FIG. 13 is a cross-sectional view of a processing step of thebackplate subsequent to the step of FIG. 12.

[0030]FIG. 14 is a cross-sectional view of emitters formed from anemitter substrate of a field emission display in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] This disclosure of the invention is submitted in furtherance ofthe constitutional purposes of the U.S. Patent Laws “to promote theprogress of science and useful arts” (Article 1, Section 8).

[0032] The present application is described with reference tofabrication techniques for structures which comprise electroniccomponents or devices. Exemplary electronic components are fabricatedfrom semiconductive substrates or substrates for flat panel or fieldemission display (FED) devices. Such substrates can comprise silicon,glass, quartz or other materials. Structures are processed andsubsequently utilized in electronic devices of various configurations.

[0033] During formation of structures such as semiconductive componentsor FED emitters, it is often necessary to form masks for variousprocessing steps. The masks can be utilized to process into a substrateor form additional layers upon the substrate. Certain aspects of thepresent invention are directed towards the formation of lithographicmasks and the formation of solutions utilized to form lithographicmasks.

[0034] Referring to FIG. 1, a structure 1 is illustrated. Processing ofstructure 1 is described with reference to formation of an electronicdevice or component. For example, structure 1 is processed to comprise atransistor, memory cell, discrete component, such as a resistor or FEDemitters in exemplary applications. Structure 1 is fabricated for use inelectronic devices in some applications.

[0035] The depicted structure 1 comprises a substrate 2 and a solutionlayer 3 formed over substrate 2. Substrate 2 comprises a semiconductivesubstrate, such as monocrystalline silicon, in some embodiments. Inparticular, substrate 2 can comprise a field emission display substrateas described below. Alternatively, substrate 2 comprises other materialssuitable for forming electronic devices or components.

[0036] Solution layer 3 comprises a medium 4 and a plurality of maskingparticles 5 within medium 4. In a preferred embodiment, medium 4comprises a photosensitive resin or material. Solution layer 3 can beformed to comprise the same solution layer as described below withreference to FIG. 5 (i.e., solution layer 42). Utilizing such asolution, masking particles 5 comprise spheres and photosensitivematerial 4 comprises photoresist. The solution is formed in theexemplary embodiment to have a concentration within an approximate rangeof 1×10⁸-1×10⁹ masking particles per milliliter of photosensitivematerial or photoresist.

[0037] In the presently described embodiment, solution layer 3 can beapplied over substrate 2 by any suitable method, such as screenprinting. Conventional offset and contact screen printing methods aredescribed below with reference to FIG. 6 and FIG. 7. Such printingtechniques are utilized in exemplary processing methods to form solutionlayer 3. As described in detail below, screen printing solution layer 3is preferred to provide a uniform distribution of spheres within layer 3and over substrate 2.

[0038] Following provision of solution layer 3 over substrate 2, medium4 comprising photosensitive material is cured or developed. Exemplarycuring methods include exposing solution layer 3 to ultraviolet light ifmedium 4 comprises positive photoresist.

[0039] Referring to FIG. 2, portions of photosensitive medium 4 areremoved following curing of exposed portions of medium 4. In particular,cured portions of photosensitive material 4 can be stripped or otherwiseremoved. Masking particles 5 remain over substrate 2 following theremoval of cured portions of medium 4.

[0040] Feet or small portions 6 of photosensitive medium 4 remainintermediate individual masking particles 5 and substrate 2 followingremoval of exposed portions of the photosensitive material. Uncuredremaining resin feet 6 assist with adhering respective masking particles5 to substrate 2.

[0041] Removal of exposed portions of photosensitive medium 4 forms amask 7 comprising masking particles 5 and feet 6. Mask 7 comprises alithographic mask for processing of structure 1 in the describedembodiment. In particular, masking particles 5 and corresponding feet 6of mask 7 define exposed regions 8 upon substrate 2. Exposed regions 8of substrate 2 can be processed in subsequent fabrication steps.

[0042] Referring to FIG. 3, an exemplary fabrication step of structure 1is described. In particular, substrate 2 is processed using maskingparticles 5 and feet 6 of mask 7 as a lithographic mask. In FIG. 3,plural diffusion regions 9 are formed within substrate 2. Exemplarydiffusion regions can comprise p type or n type diffusion regionsdepending upon the particular structure 1 being processed.

[0043] Such diffusion processing is exemplary and other processing stepssuch as deposition can occur using mask 7. Following formation ofdiffusion regions 9, or other alternative processing, masking particles5 and feet 6 can be stripped from substrate 2. Acetone is utilized inone embodiment to strip masking particles 5 and feet 6.

[0044] Referring to FIG. 4-FIG. 14, methods of forming masks aredescribed with reference to field emission display devices. Further,methods of forming field emission display emitters are described. Theinvention is not limited to field emission display device fabrication asdescribed in the following embodiments and applications. Aspects of thepresent invention described below might be utilized within any maskingand etching process.

[0045] Referring to FIG. 4, an exemplary portion of a field emissiondisplay 10 is depicted. The illustrated portion of the field emissiondisplay 10 includes a display segment 12. Display segment 12 is capableof displaying a pixel of information, or a portion of a pixel. Forexample, display segment 12 may be configured to display one green dotof a red/green/blue fall-color triad pixel. Field emission display 10includes a faceplate or screen 24 and a cathode plate or baseplate 28spaced therefrom. Support structures or separators 30 space faceplate 24from baseplate 28 and generally define segment 12 in the illustratedembodiment.

[0046] Baseplate 28 of the described embodiment comprises a matrixaddressable array of cathode emission structures or emitters 16.Baseplate 28 additionally includes an emitter substrate 14, upon whichthe emission structures 16 are created, a dielectric insulating layer26, and an anodic grid 18.

[0047] Emitter substrate 14 has been patterned and etched to formmicro-cathodes or emitters 16 as described in detail below. Displaysegment 12 includes plural field emission sites 15. Sites 15 correspondto the emitters 16. Dielectric insulating layer 26 is formed uponsubstrate 14 intermediate emitters 16 and sites 15. More specifically,insulator 26 has plural openings at the field emission sites 15. Avacuum is created between faceplate 24 and baseplate 28 to provideproper functioning of plural emitters 16 of the described field emissiondisplay 10. Separators 30 function to support atmospheric pressure whichexists on electrode faceplate 24 as a result of the vacuum.

[0048] Emitters 16 are constructed on top of emitter substrate 14.Emitters 16 are integral with emitter substrate 14 and individuallycomprise a cathode for emission of electrons. Alternatively, emitters 16form cathodes from one or more deposited conductive films, such as achromium amorphous silicon bilayer. Emitters 16 preferably have a finemicro-point in the described embodiment.

[0049] Grid structure 18 surrounds emission sites 15 in the describedembodiment. A power source 20 is utilized to apply a voltagedifferential between the cathodes (emitters 16) and anodic grid 18. Inparticular, emitters 16 are individually electrically coupled with anegative terminal of source 20. A positive terminal of source 20 iscoupled with grid 18. Grid 18 serves as a structure for applying anelectrical field potential to appropriate emitters 16. A stream ofelectrons 22 is emitted from emitters 16 responsive to the applicationof a voltage differential via grid 18.

[0050] A second positive terminal of source 20 is connected withfaceplate 24 thereby forming another anode. Faceplate 24 includes aphosphor coating 25 over surface facing emitters 16. Electrons ejectedfrom emitters 16 are aimed toward faceplate 24. Further details of fieldemission displays are described in U.S. Pat. Nos. 5,229,331 and5,391,259, both incorporated herein by reference.

[0051] Referring to FIG. 5, fabrication of an exemplary portion ofbaseplate 28 of a field emission display is shown. In particular,methods of forming field emission display masks utilized for formationof emitters 16 are described. Methods of forming emission displayemitters 16 are also described. The formed emitters 16 are conical inthe described embodiment. Emitters 16 may comprise protuberances ofother shapes in other embodiments.

[0052] The illustrated baseplate 28 includes emitter substrate 14, amasking layer 40 and a layer of solution 42. A single crystal siliconlayer serves as substrate 14 in one embodiment. Amorphous silicon orpolysilicon deposited upon a glass substrate are other examples. Othermaterials are utilized in other embodiments. In particular, substrate 14of FIG. 5 can be any material from which emitters 16 can be fabricated.

[0053] Masking layer 40, also referred to as a hardmask layer, comprisesa masking layer substrate which is deposited or grown on substrate 14 inthe described embodiment. An example material for layer 40 is silicondioxide. Masking layer 40 preferably has a thickness great enough toavoid being completely consumed during subsequent etching processes. Itis also desired to provide a masking layer 40 which is not excessivelythick so as to overcome adherent forces which maintain the masking layerin the correct position with respect to emitters 16 throughout theemitter fabrication process as described hereafter. An exemplary rangeof thicknesses of masking layer 40 is 0.05-0.5 microns with a thicknessof 0.2 microns being preferred.

[0054] Solution layer 42 comprises a plurality of masking particles 46within a medium 48. In one embodiment, masking particles 46 areinitially mixed into a fairly viscous or thixotropic medium 48. Medium48 is preferably liquid having an operable viscosity range from 10 to1100 centipoise. A viscosity range from 40 to 200 centipoise ispreferred at room temperature. Solution layer 42 is screen printed ontoa surface of masking layer 40 and subsequently cured. As describedbelow, medium 48 is thereafter removed providing an etch mask forfabricating another mask used to form a random array of field emittertips (i.e., emitters).

[0055] Masking particles 46 preferably comprise spherical members andmedium 48 comprises photoresist or photo sensitive material such aspolyimide. Example materials are polystyrene or latex for spheres 46 andpositive photoresist for medium 48. Masking particles 46 have anexemplary diameter of approximately one micron (0.04 mils). A preferredspherical diameter range is from 0.5 to 2.0 microns.

[0056] Masking members or particles 46 are typically provided in a watersolution having a density of approximately 10¹¹ beads or spheres permilliliter (ml) of solution. Exemplary bead solutions are available fromBangs Labs IDC Corp. The water solution containing the beads or maskingparticles 46 is dissolved in a carrier, such as isopropyl alcohol, andsubsequently combined or mixed with photoresist in one embodiment of theinvention. In one example, two cubic centimeters (cc) of isopropylalcohol were added per one cubic centimeter of bead solution. Then, fivecubic centimeters of photoresist were combined with this solutionproviding a ratio of 1:2:5 by volume. An exemplary ratio range of beadsolution to isopropyl alcohol to photoresist is 1:(2 20):(5 50).

[0057] A 1:2:5 mixture of solution yields a bead or masking particledensity of approximately 1.25×10¹⁰ beads per milliliter of solution. Anexemplary preferred concentration of masking particles 46 within medium48 is within the approximate range of 1×10⁸-1×10⁹ beads/ml immediatelyprior to screen printing upon hardmask masking layer 40.

[0058] In one example, approximately 1×10¹¹ spheres were mixed intoapproximately 300 ml of Olin HPR504 resist comprising medium 48. Thesolution containing spheres 46 and medium 48 was screen printed onto aglass substrate using conventional screen printing to form solutionlayer 42. A 400 mesh screen having a wire diameter of 0.00075 incheswith a patterned emulsion coating of 0.0002 inches was utilized for thescreen printing.

[0059] A screen 44 is utilized to screen print the solution layer 42 inaccordance with the described embodiment of the present invention. It isdesired to provide solution layer 42 upon masking layer 42 having auniform density of masking particles 46. It is also preferred to providespacing between adjacent masking particles 46.

[0060] Screen 44 includes plural mesh portions 45 (one whole meshportion 45 is shown in FIG. 5). Mesh portions 45 of screen 44 definepredefined regions 50 over masking layer 40 and emitter substrate 14(one predefined region 50 corresponding to the illustrated mesh portion45 is shown in FIG. 5). Screen 44 includes mesh portions 45 individuallyhaving dimensions of 1.75 mils by 1.75 mils square in one example.Screen 44 is thin as possible in preferred embodiments. An exemplarypreferred thickness for a cured layer 42 is about five microns.

[0061] Referring to FIG. 6, conventional offset screen printing ofsolution to form solution layer 42 is shown. A squeegee 41 is used tourge solution through mesh portions of screen 44. Solution is depositedonto screen 44 in front of the direction of travel of squeegee 41 in thedescribed embodiment. Screen 44 and masking layer 40 are spaced by adistance d₁ (e.g., 0.04 inches). Squeegee 41 passes laterally overscreen 44 and presses screen 44 to contact the layer being printed upon(e.g., masking layer 40). Squeegee 41 simultaneously forces the solutioncontaining masking particles through mesh portions of screen 44.

[0062] Referring to FIG. 7, contact printing of the solution to formsolution layer 42 upon masking layer 40 is shown. Screen 44 contactsmasking layer 40 when contact printing is utilized. Squeegee 41 passeslaterally over screen 44 forcing the solution containing the maskingparticles through mesh portions of screen 44. Conventional offsetprinting is the preferred screen printing method.

[0063] Referring to FIG. 8, a top view of solution layer 42 and screen44 are shown. Plural mesh portions 45 (shown in phantom) are defined byscreen 44. Screen 44 also defines plural regions 50 over the maskinglayer and the emitter substrate (the emitter substrate and the maskinglayer are below solution layer 42 and not shown in FIG. 8). Predefinedregions 50 correspond to mesh portions 45 in the illustrated embodiment.In accordance with one aspect of the present invention, mesh portions 45of screen 44 operate to guide masking particles 46 to respectivepredefined regions 50 over emitter substrate 14 and masking layer 40.The prior art is not understood to disclose any mechanism to guidemasking particles over the region(s) to be covered with maskingparticles.

[0064]FIG. 8 illustrates an exemplary number of masking particles 46within respective predefined regions 50. More or less masking particles46 can be provided within individual predefined regions 50. In apreferred embodiment, a two micron pitch of masking particles 46 isdesired if masking particles 46 having a diameter of one micron areutilized. In this embodiment, the approximate number of maskingparticles 46 received through one mesh portion 45 is the area of themesh portion in square microns divided by four. Further, FIGS. 5 and 8diagrammatically illustrate screen printing of masking particles 46 andare not to scale.

[0065] Referring to FIG. 9, screen 44 is removed from backplate segment28 following formation of solution layer 42 over emitter substrate 14.Screen 44 is ideally removed before substantial curing of solution layer42. Masking particles 46 and medium 48 flow to fill the void created bythe removal of screen 44.

[0066] Backplate segment 28, including emitter substrate 14, maskinglayer 40 and solution layer 42, is preferably agitated following removalof screen 44 and prior to substantial curing. Such agitation encouragesmovement of masking particles 46 apart from one another and providesspacing intermediate adjacent masking particles 46. Such agitation alsoencourages settling of masking particles 46 upon masking layer 40.Masking particles 46 may also adhere to masking layer 40 followingcontacting of the same. Subsequently, solution layer 42 is cured. Anexample curing process includes air drying backplate 28 for twentyminutes in ambient air at 50% humidity. Masking particles 46 defineintermediate portions 54 of medium 48 between adjacent masking particles46.

[0067] Referring to FIG. 9 and FIG. 10, following curing of solutionlayer 42, medium 48, including intermediate portions 54 thereof, isstripped or otherwise removed. In embodiments where medium 48 comprisespositive photoresist, baseplate segment 28 is flood exposed toultraviolet light and developed. Media 48, including intermediateportions 54, is thereafter stripped. A foot or small portion 52 ofmedium 48 can remain intermediate individual masking particles 46 andmasking layer 40. Feet 52 of medium 48 are defined by the diameter ofrespective masking particles 46. Masking particles 46 preferably contactmasking layer 40. Remaining portions of medium 48 or feet 52 assist withadhesion of bases of masking particles 46 to masking layer 40. Maskingparticles 46 and feet 52 form a mask 59 upon masking layer 40. Inparticular, masking particles 46 and feet 52 define plural exposedportions or regions 58 of masking layer 40.

[0068] Referring to FIG. 10 and FIG. 11, exposed portions 58 of maskinglayer 40 are removed from emitter substrate 14 using spheres 46 as mask59. In one embodiment, anisotropic etching is utilized. An examplechemistry includes CF₄, CHF₃, Ar₂ as described in the '259 patent. Suchremoval of exposed portions 58 of masking layer 40 provides maskingelements 56 beneath masking particles 46. Masking elements 56substantially correspond to, or are defined by, the diameters ofrespective masking particles 46. Masking elements 56 are circular in thedescribed embodiment. Utilization of masking particles 46 in accordancewith the present invention improves critical dimension control whileproducing masking elements 56.

[0069] Referring to FIG. 12, the beads or masking particles and the feethave been stripped from masking elements 56. Acetone is utilized in oneembodiment to strip the masking particles and feet. Masking elements 56define a mask 57, which is also referred to herein as a hardmask.Masking elements 56 define exposed regions or portions 60 of emittersubstrate 14. Exposed portions 60 are intermediate masking elements 56.

[0070] Referring to FIG. 13, portions of emitter substrate 14, includingexposed portions 60, have been etched (preferably substantiallyisotropically) to form plural emitters 16. An example etching chemistryis SF₆, Cl₂, He as set forth in the '259 patent. Emitters 16 are formedcorresponding to circular masking elements 56. A timed etch is utilizedto form emitters 16 in one embodiment.

[0071] Referring to FIG. 14, a substantially uniform array 62 ofemitters 16 is shown upon emitter substrate 14. The insulatingdielectric layer may be subsequently formed to fabricate the backplate28 shown in FIG. 4. Additionally, the anodic grid may be providedenabling control of the emission of electrons from emitters 16.

[0072] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A lithographic mask forming solution comprising: a photosensitivematerial; and a plurality of masking particles within the photosensitivematerial.
 2. The solution according to claim 1 wherein thephotosensitive material comprises photoresist.
 3. The solution accordingto claim 1 wherein the solution has a concentration within anapproximate range of 1×10⁸-1×10⁹ masking particles per milliliter ofphotosensitive material.
 4. A structure comprising: a substrate; and alayer of solution provided over the substrate, the solution comprising aphotosensitive material and a plurality of masking particles.
 5. Thestructure according to claim 4 wherein the layer of solution is screenprinted over the substrate.
 6. The structure according to claim 4wherein the substrate comprises a field emission display substrate. 7.The structure according to claim 4 wherein the photosensitive materialcomprises photoresist.
 8. The structure according to claim 4 wherein thesubstrate comprises a field emission display substrate and thephotosensitive material comprises photoresist.
 9. A structure formingmethod comprising: providing a solution including photosensitivematerial and a plurality of masking particles; applying the solutionover a substrate; removing at least a portion of the photosensitivematerial while leaving the masking particles over the substrate; andprocessing the substrate using the masking particles as a mask.
 10. Themethod according to claim 9 wherein the applying comprises screenprinting the solution over the substrate.
 11. The method according toclaim 9 wherein the substrate comprises a field emission displaysubstrate.
 12. The method according to claim 9 wherein the substratecomprises a semiconductive substrate.
 13. The method according to claim9 wherein the method comprises an electronic device forming method. 14.The method according to claim 9 further comprising adhering the maskingparticles over the substrate using the photosensitive material.
 15. Themethod according to claim 9 further comprising removing the maskingparticles following the processing.
 16. The method according to claim 9wherein the providing comprises providing a solution includingphotosensitive material comprising photoresist.
 17. A structure formingmethod comprising: providing a solution including photosensitivematerial and a plurality of masking particles within the photosensitivematerial; screen printing a layer of the solution over a substrate;curing at least a portion of the photosensitive material screen printedover the substrate; removing cured photosensitive material while leavingthe masking particles over the substrate; and processing the substrateusing the masking particles as a mask.
 18. The method according to claim17 wherein the substrate comprises a field emission display substrate.19. The method according to claim 17 wherein the substrate comprises asemiconductive substrate.
 20. The method according to claim 17 furthercomprising adhering the masking particles over the substrate using thephotosensitive material.
 21. The method according to claim 17 furthercomprising removing the masking particles following the processing. 22.The method according to claim 17 wherein the providing comprisesproviding a solution including photosensitive material comprisingphotoresist.
 23. A mask forming method comprising: providing a solutionincluding photosensitive material and a plurality of masking particleswithin the photosensitive material; applying the solution over asubstrate; curing at least a portion of the photosensitive materialapplied over the substrate; and removing cured photosensitive materialwhile leaving the masking particles over the substrate.
 24. The methodaccording to claim 23 wherein the applying comprises screen printing thesolution over the substrate.
 25. The method according to claim 23wherein the applying comprises applying the solution over asemiconductive substrate.
 26. The method according to claim 23 whereinthe applying comprises applying the solution over a masking layersubstrate.
 27. The method according to claim 23 further comprisingadhering the masking particles over the substrate using thephotosensitive material.
 28. The method according to claim 23 whereinthe providing comprises providing a solution including photosensitivematerial comprising photoresist.
 29. A lithographic mask solutionforming method comprising: providing a photosensitive material;providing a plurality of masking particles; and mixing the maskingparticles with the photosensitive material.
 30. The method according toclaim 29 further comprising mixing the masking particles with a carrier.31. The method according to claim 29 wherein the providing thephotosensitive material comprises providing photoresist.
 32. A maskforming method comprising: forming a masking layer over a surface of asubstrate; screen printing plural masking particles over a surface ofthe masking layer; and removing at least portions of the masking layerusing the masking particles as a mask.
 33. The method according to claim32 wherein the screen printing comprises offset screen printing.
 34. Themethod according to claim 32 further comprising removing the maskingparticles following the removing.
 35. The method according to claim 32further comprising agitating the masking particles following the screenprinting.
 36. The method according to claim 32 wherein the screenprinting comprises printing spherical masking particles.
 37. The methodaccording to claim 32 wherein the screen printing comprises printingmasking particles within a solution containing photoresist.
 38. Themethod according to claim 37 further comprising: curing the photoresist;and removing portions of the photoresist from over the masking particlesand masking layer.
 39. The method according to claim 37 wherein thescreen printing comprises printing masking particles within a solutionhaving a concentration within an approximate range of 1×10⁸-1×10⁹masking particles per milliliter of photoresist.
 40. The methodaccording to claim 32 further comprising guiding the spherical maskingparticles over predefined regions of the masking layer by the screenprinting.
 41. The method according to claim 32 wherein the removingforms discrete circular masking elements.
 42. The method according toclaim 32 wherein the removing comprises anisotropically etching themasking layer.
 43. The method according to claim 32 wherein the formingcomprises forming a masking layer over an emitter substrate of a fieldemission display.
 44. A mask forming method comprising: forming amasking layer over a surface of a substrate; forming a layer of maskingparticles over a surface of the masking layer; providing the maskingparticles over predefined regions of the surface of the substrate duringthe forming; and removing at least portions of the masking layer usingthe masking particles as a mask.
 45. The method according to claim 44further comprising removing the masking particles following theremoving.
 46. The method according to claim 44 further comprisingagitating the masking particles following the providing.
 47. The methodaccording to claim 44 wherein the providing comprises printing themasking particles using a screen.
 48. The method according to claim 44wherein the providing comprises screen printing masking particles withina solution containing photoresist.
 49. The method according to claim 48further comprising: curing the photoresist; and removing portions of thephotoresist from over the masking particles and masking layer.
 50. Themethod according to claim 44 wherein the removing comprisesanisotropically etching the masking layer.
 51. The method according toclaim 44 wherein the forming comprises forming a masking layer over anemitter substrate of a field emission display.
 52. A mask forming methodcomprising: forming a masking layer over a surface of a substrate;forming a layer of solution including plural masking particles over asurface of the masking layer; guiding the masking particles topredefined regions over the substrate using a screen; and removing atleast portions of the masking layer using the masking particles as amask.
 53. The method according to claim 52 further comprising agitatingthe masking particles following the guiding.
 54. The method according toclaim 52 wherein the forming a masking layer comprises forming a maskinglayer over an emitter substrate of a field emission display.
 55. Themethod according to claim 52 wherein the forming the layer of solutioncomprises screen printing masking particles within photoresist.
 56. Themethod according to claim 55 further comprising: curing the photoresist;and removing portions of the photoresist from over the masking particlesand masking layer.
 57. The method according to claim 52 wherein theremoving comprises anisotropically etching the masking layer.
 58. Afield emission display emitter mask forming method comprising: forming amasking layer over a surface of an emitter substrate; printing a layerof masking particles over a surface of the masking layer using a screen;removing portions of the masking layer intermediate the screen printedmasking particles; and removing the masking particles from remainingportions of the masking layer following the removing of portions of themasking layer.
 59. The method according to claim 58 further comprisingremoving the screen following the printing and prior to the removing theportions of the masking layer.
 60. The method according to claim 58further comprising agitating the masking particles following theprinting.
 61. The method according to claim 58 wherein the printingcomprises printing the masking particles within a solution containingphotoresist.
 62. The method according to claim 61 further comprising:curing the photoresist; and removing portions of the photoresist fromover the masking particles and masking layer.
 63. The method accordingto claim 58 wherein the removing portions of the masking layer comprisesanisotropically etching the masking layer.
 64. A method of formingplural field emission display emitters comprising: forming a maskinglayer over an emitter substrate; screen printing a plurality of maskingparticles over the masking layer; removing portions of the masking layerintermediate the screen printed masking particles to form a plurality ofmasking elements comprising the masking layer; removing the maskingparticles from the masking elements; and removing portions of theemitter substrate using the masking elements as a mask to form pluralemitters.
 65. The method according to claim 64 further comprisingremoving a screen following the printing.
 66. The method according toclaim 64 further comprising agitating the masking particles followingthe screen printing.
 67. The method according to claim 64 wherein thescreen printing comprises printing masking particles within a solutioncontaining photoresist.
 68. The method according to claim 67 furthercomprising: curing the photoresist; and removing portions of thephotoresist from over the masking particles and masking layer.
 69. Themethod according to claim 64 further comprising guiding the sphericalmasking particles over predefined regions of the masking layer by thescreen printing.
 70. The method according to claim 64 wherein theremoving portions of the emitter substrate comprises removing using themasking elements.
 71. The method according to claim 64 wherein theremoving portions of the masking layer comprises anisotropically etchingthe masking layer.
 72. The method according to claim 64 wherein theremoving portions of the emitter substrate comprises removing using anisotropic etch.
 73. A method of forming a substantially uniform array ofemitters upon an emitter substrate during field emission displayfabrication comprising: providing an emitter substrate; forming ahardmask layer over the emitter substrate; providing a solutioncontaining a plurality of spherical masking particles and photoresist,the solution having a concentration within an approximate range of1×10⁸-1×10⁹ masking particles per milliliter of photoresist; forming alayer of the solution including the spherical masking particles andphotoresist upon a surface of the hardmask layer, the forming of thelayer including: guiding the spherical masking particles to predefinedregions over the surface of the hardmask layer using a screen; removingthe screen; agitating the layer of solution formed upon the surface ofthe hardmask layer; and curing the layer of solution following theagitating; stripping portions of the photoresist intermediate thespherical masking particles following the forming of the layer of thesolution; etching portions of the hardmask layer intermediate the screenprinted spherical masking particles using an anisotropic etch therebyforming a plurality of circular masking elements beneath the sphericalmasking particles; stripping the spherical masking particles from thecircular masking elements; and etching portions of the emitter substrateto form plural emitters corresponding to the circular masking elementsusing an isotropic etch.